Weathering testing device



June s, 194s. R AWE 2,442,759

WEATHERING TESTING DEVICE Filed NOV. 19, 1945 NVENTOR. Rob erf .DGV/

ATTORNEY Patented June 8, 1948 UNITED STATES PATENT OFFICE (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 7 Claims.

This invention relates to a weathering testing device.

It is an object ci this invention to provide a device wherein an atmosphere of controlled temperature and humidity can be maintained over extended periods of time.

Another object is to provide a device wherein accelerated weathering tests at relatively high temperatures and humidities can be conducted.

Further objects and advantages of this invention, as Well as its construction, arrangement and operation, will be apparent from the following description and claims in connection with the accompanying drawing, in Which the ligure is a sectional view of a device embodying the principles of this invention.

The device comprises an outer housing II defining a chamber and constructed of insulating materials of suicient thickness to prevent appreciable passage of heat therethrough. Substantially centered within outer housing II in spaced relation therefrom and concentrically enclosed thereby is an inner housing I2 deiining a chamber and made of sheet steel or similar semiconducting material permitting appreciable heat transfer therethrough by conduction. Shelves I3, of wire screen or similar material not seriously affecting the circulation oi air therethrough, are desirably provided within inner housing I2. Both housings II and I2 are provided with adjacent access doors (not shown), which can be provided with double-paned glass windows to permit observation oi the interior of the inner housing I2 from the exterior of the outer housing I I.

Approximately centered in the lower surface of outer housing I I is a vent I4, which also serves as a drain. An opening I5 is provided in the lower surface of inner housing I2, preferably directly above vent I 4. A plurality of vents I are provided in the sides of housings II and E2 near the tops thereof. Vents I6 can be provided with adjustable apertures, to regulate the flow of air therethrough.

Heat is v'supplied to the device in the lower space betweenouter housing II and inner housing I2, as by electrical resistance I?. Resistance l'lis preferably automatically controlled, as thermostat ES, the location of the automatic control device being above resistance I'I but outside inner housing I2. Water pan I9, which can be kept lled to constant level by means oi' tube 29, rests upon pad 2l, near the bottom of the interior of inner housing I2, andpreferably directly above opening I5. Water pan I9 can serve as a constant source of water vapor through the insertion of an immersion heater therein, illustrated as electrical resistance 22, controlled by rheostat 23 located outside outer housing II. Conventional devices indicating temperature and humidity can be employed in the interior of inner housing I2, and can be connected to indicating and recording devices outside outer housing I I, or can be observed through glass inserts in the access doors or walls of housings II and I2.

The device functions in the following manner. A plurality of objects which are to be subjected to an extended test at elevated temperatures and humidities are placed upon the shelves I3, and the access doors to housings II and I2 closed and locked. Thermostat I8 is then adjusted and current allowed to iiow through electrical resistance I'I' until the desired temperature is attained in the interior of inner housing I2. This may require readjusting of the thermostat I8 after observing stabilization of the temperature inside inner housing I2. The temperature governing thermostat I8, that is the temperature below inner housing I2, is not the same as the temperature in the interior oi-inner housing I2, but it has been found that a more constant temperature is maintained in the interior of inner housing I2 by control regulated by the temperature outside the inner housing. Once the interior of inner housing I2 has achieved equilibrium at the desired temperature, thermostat I8 is adjusted to maintain the equilibrium.

After equilibrium at the desired temperature is achieved in the interior of inner housing I2, the desired relative humidity is provided by evaporation of water vapor from water pan I9. The evaporation is caused by the passage of current through electrical resistance 22. The rate of evaporation is controlled by rheostat 23, rheostat 23 bang adjusted in accordance with the relative humidity in the interior of inner*v housing I2 until an equilibrium is achieved at the desired value.

Once adjusted to achieve the desired temperature and'relative humidity, the device maintains these conditions with extremely small variations for an indefinite period of time. The location of the heat source, electrical resistance I1, at the bottom of outer housing II causes convection through the device, resulting in a steady circulation of air through housings II and I2, the air entering through vents I4 and I5 and exiting through vents I 6. This circulation of air can be limited by adjusting the openings in vents I6. Once equilibrium has been attained in inner housing I2, the circulation of air through temperatures than is thermostat I8. and is relatively less aiected thereby.

Constancy of temperature within housing I2, and thereby constancy of relative humidity, is also contributed to by the manner in 'which heat input to the housing I2 is achieved. VI-leat can enter inner housing I2 by convection through opening I5, by radiation through opening i5 and through fluctuations in ambient temperatureY and other variables. It is desirable that the heat input to the interior of inner housing I2 by conduction through the walls of housing I2 be a considerable proportion of the total input. For this reason the walls of housing I2 are desirably made of material and of a thickness having moderateheat transference properties. Such a semi-conducting material is sheet steel, thicknessesgof from 1/a" toi" having been found especially suitable. vRelatively thin walls of material having high heat conducting properties, such as copper, have been found to be unsuitable, causing the proportion of heat input to housing VI2 by conduction to be disproportionately large and affecting the constancy of temperature which may be maintained within housing I2.- Similarly, the use ofA materials of high insulating properties in the walls of housing I2, such as asbestos-board, results in the proportion of heat input into into housing I2 by conduction to be disproportionately small and detrimently aects the constancy of temperature which may be maintained. Y

It is to be understood that various modications and changes may be made in this invention Without departing from theA spirit and scope thereof as set Vforth in the appended claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. A device for providing Van atmosphere of controlled temperature and humidity comprising two concentric, spaced housings, heating means within the space between said housings, and humidifying means within the inner of said housings.

2. A device for providing an atmosphere of controlledtemperature and humidity comprising two concentric, spaced housings, thermostatically controlled electrical heating means within the space between said housings, and controlled A said housings. W4. A device for providing an Vto humidifying means within the inner of said housings. Y 3. A device for providing an atmosphere of controlled temperature and humidity comprising an outer insulating housing, an inner housing of semi-conducting material contained Within said outer housing in spaced relation therefrom, thermostatically controlled electrical heating means within the space between said housings, and oontrolled humidifying means within the inner of atmosphere of controlled temperature and humidity comprising an outer insulating housing, an inner housing of semi-conducting material contained within said outer housing in spaced relation therefrom, said inner housing being open to said outer housing throughv an opening at its bottom, thermostatically controlled electrical heating means within thespace between said housings directly below said inner housings, and controlled humidifying means within said inner housing.

5. A device for providing an atmosphere of controlled temperature' and humidity comprising an outer insulating housing, an inner housing of semi-conducting material contained within said outer housing in spaced relation therefrom, said inner housing being 'open to said outer housing through an opening at its bottom, electrical heating means within the space between said housings directly below said inner housing, said heating means being controlled by a thermostat above said heating means but outside said inner housing,

and controlled humidifying means `within said f Ycontrolled temperature and humidity comprisingv two substantially concentric, spaced housings, heating means within the space between said housings, and humidifying means within said housings.

ROBERT DAVIE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,967,185 Clapp July 17, 1934 2,201,389

De Give May 21, 1940 

